Optical disk, and method and apparatus for reproducing information recorded in optical disk

ABSTRACT

An optical disk is provided for recording data of a signal modulated according to a predetermined modulation method in a form of concavo-convex pits. The optical disk includes a first area having a reflecting film partly removed, and a second area for recording pits which are different from pits satisfying requirements of the predetermined modulation method. The first area having the reflecting film partly removed includes a portion which is formed by removing the reflecting film, and has a length longer than a maximum pit length determined by the modulation method in a circumferential direction of the optical disk. When the pits recorded on the optical disk are physically copied as they are, physical copying of the optical disk can be prevented by utilizing such a difference that the authorized optical disk differs from a pirated copy in a combination of the respective reproduced signals of the first and second areas.

[0001] This application is a divisional application of Ser. No.09/677,595, filed Oct. 3, 2000.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an optical disk for recordingcopyrighted content information, and a method and an apparatus forreproducing copyrighted content information recorded in an optical disk.

[0004] 2. Description of the Related Art

[0005] In recent multimedia societies, optical disks such as a CD-ROMand a DVD have become remarkably widespread. With the widespread use ofthe optical disks, so-called pirated ROM disks have appeared and allowsa pirate to benefit from the disk without compensating a copyright ownerby fraud by illegally making a pirated copy of the optical disk. Thepercentage of pirated copies of disks is rapidly increasing. Illegalcopying of the optical disk can take place in the following manner.Generally speaking, a pirate purchases an authorized optical disk, makesa master tape by reproducing information recorded on the optical disk bymeans of a disk drive, and mass-produces the pirated copies from themaster tape by the same method as a general disk manufacturing method.

[0006] In order to protect against the above-mentioned unauthorizedcopying, some optical disks are devised so that they can be reproducedby only a player designed specifically for them. As this type of opticaldisk, for example, there is, disclosed in the Japanese Patent Laid-OpenPublication No 7-85574 a method including the steps of recording maininformation on an optical recording medium using a predetermined codingmeans, storing key information indicating decoding means for decodingthe main information in a form of a barcode symbol in a mirror surfacearea or the like, reading our the key information by a reproducingapparatus, decoding and reproducing the main information utilizing acoding method indicated by the key information.

[0007] The above-mentioned method of protecting against unauthorizedcopying has such a very excellent advantage that a general optical diskplayer cannot reproduce the optical disk. However, the method ishelpless against and cannot protect against copying means for performingcopying involving no reproducing operation, i.e., for physically copyingor transferring concavo-convex pits of data of a signal recorded on anoptical disk surface as they are. This copying method requires noreproducing means, and can copy concavo-convex pit information of theoptical disk as it is even though original data of signal to be recordedon the optical disk is made sophisticated and complicated. Therefore,the above mentioned method of protecting against unauthorized copying isuseless.

SUMMARY OF THE INVENTION

[0008] An essential object of the present invention is, therefore, toprovide an optical capable of protecting against copying means forphysically copying concavo-convex pits of data of a signal recorded onan optical disk surface as they are.

[0009] Another object of the present invention is to further provide anmethod and apparatus for reproducing information recorded on the opticaldisk. capable of protecting against copying means for physically copyingconcavo-convex pits of data of a signal recorded on an optical disksurface as they are.

[0010] In order to achieve the aforementioned objective, according toone aspect of the present invention, there is provided an optical diskfor recording data of a signal modulated according to a predeterminedmodulation method in a form of concavo-convex pits, the optical diskcomprising:

[0011] a first area having a reflecting film partly removed; and

[0012] a second area for recording pits which are different from pitssatisfying requirements of the predetermined modulation method.

[0013] According to another aspect of the present invention, there isprovided an optical disk for recording data of a signal modulatedaccording to a predetermined modulation method in a form ofconcavo-convex pits, the optical disk comprising:

[0014] a first area having a reflecting film partly removed;

[0015] a second area for recording pits which are different from pitssatisfying requirements of the predetermined modulation method;

[0016] a first area location information recording area for recordinglocation information of the first area on the disk; and

[0017] a second area location information recording area for recordinglocation information of the second area on the disk.

[0018] In the above-mentioned optical disk, the first area having thereflecting film partly removed is preferably included in a user datarecording area for recording user data therein.

[0019] In the above-mentioned optical disk, the first area having thereflecting film partly removed preferably includes a portion, which isformed by removing the reflecting film, and which has a length longerthan a maximum pit length determined by the requirements of themodulation method, in a circumferential direction of the optical disk.

[0020] In the above-mentioned optical disk, each of the pits recorded inthe second area is preferably longer than a maximum pit lengthdetermined by the modulation method.

[0021] In the above-mentioned optical disk, each of the pits recorded inthe second area is preferably longer than a maximum pit lengthdetermined by the modulation method, and

[0022] wherein edges in the center of each of the pits recorded in thesecond area are inclined more gradually than edges in an end portion ofeach of the pits.

[0023] In the above-mentioned optical disk, the first area locationinformation recording area and the second area location informationrecording area are preferably recorded in an area except for a user datarecording area for recording user data therein.

[0024] According to a further aspect of the present invention, there isprovided a method for reproducing information recorded on an opticaldisk which is provided for recording data of a signal modulatedaccording to a predetermined modulation method in a form ofconcavo-convex pits, the optical disk comprising a first area having areflecting film partly removed, and a second area for recording pitswhich are different from pits satisfying requirements of thepredetermined modulation method, the method including the steps of:

[0025] detecting an area having the reflecting film partly removed, inaccordance with a reproduced signal of the first area;

[0026] detecting a pit which is different from the pit satisfying therequirements of the predetermined modulation method, in accordance witha reproduced signal of the second area; and

[0027] judging whether or not the information recorded on the opticaldisk should be reproduced, in accordance with results detected by thetwo steps of detecting.

[0028] According to a still further aspect of the present invention,there is provided a method for reproducing information recorded on anoptical disk which is provided for recording data of a signal modulatedaccording to a predetermined modulation method in a form ofconcavo-convex pits, the optical disk comprising a first area having areflecting film partly removed, a second area for recording pits whichare different from pits satisfying requirements of the predeterminedmodulation method, a first area location information recording area forrecording location information of the first area on the disk, and asecond area location information recording area for recording locationinformation of the second area on the disk, the method including thesteps of:

[0029] reproducing information recorded in the first area in accordancewith the location information of the first area on the disk recorded inthe first area location information recording area, and outputting areproduced signal of the first area;

[0030] reproducing information recorded in the second area in accordancewith the location information of the second area on the disk recorded inthe second area location information recording area, and outputting areproduced signal of the second area;

[0031] detecting an area having the reflecting film partly removed, inaccordance with the reproduced signal of the first area;

[0032] detecting a pit which is different from the pit satisfying therequirements of the predetermined modulation method, in accordance withthe reproduced signal of the second area; and

[0033] judging whether or not the information recorded on the opticaldisk should be reproduced, in accordance with results detected by thetwo steps of detecting.

[0034] In the above-mentioned method, the step of reproducinginformation recorded in the first area preferably includes the step ofreproducing information recorded in the first area in a defocus state.

[0035] In the above-mentioned method, the step of reproducinginformation recorded in the first area preferably includes the step ofreproducing the information recorded in the first area by performingtracking an area located between two adjacent tracks.

[0036] In the above-mentioned method, the step of detecting the areahaving the reflecting film partly removed preferably includes the stepof detecting whether or not the reflecting film is removed on the twoadjacent tracks.

[0037] According to a still further aspect of the present invention,there is provided an apparatus for reproducing information recorded onan optical disk which is provided for recording data of a signalmodulated according to a predetermined modulation method in a form ofconcavo-convex pits, the optical disk comprising a first area having areflecting film partly removed, and a second area for recording pitswhich are different from pits satisfying requirements of thepredetermined modulation method, the apparatus comprising:

[0038] a first area detecting circuit for detecting the first area inaccordance with a reproduced signal from the optical disk uponreproducing information recorded in the first area, and outputting afirst detecting signal;

[0039] a second area detecting circuit for detecting the second area inaccordance with a reproduced signal from the optical disk uponreproducing information recorded in the second area, and outputting asecond detecting signal; and

[0040] judging means for judging whether or not the information recordedon the optical disk should be reproduced, in accordance with the firstand second detecting signals.

[0041] According to a still further aspect of the present invention,there is provided an apparatus for reproducing information recorded onan optical disk which is provided for recording data of a signalmodulated according to a predetermined modulation method in a form ofconcavo-convex pits, the optical disk comprising a first area having areflecting film partly removed, a second area for recording pits whichare different from pits satisfying requirements of the predeterminedmodulation method, a first area location information recording area forrecording location information of the first area on the disk, and asecond area location information recording area for recording locationinformation of the second area on the disk, the apparatus comprising:

[0042] a first detecting window generating circuit for generating afirst detecting window signal in accordance with the locationinformation of the first area on the disk recorded in the first arealocation information recording area;

[0043] a second detecting window generating circuit for generating asecond detecting window signal in accordance with the locationinformation of the second area on the disk recorded in the second arealocation information recording area;

[0044] a first area detecting circuit for detecting the first area inaccordance with a reproduced signal from the optical disk uponreproducing information recorded in the first area, and outputting afirst detecting signal;

[0045] a second area detecting circuit for detecting the second area inaccordance with a reproduced signal from the optical disk uponreproducing information recorded in the second area, and outputting asecond detecting signal; and

[0046] judging means for judging whether or not the information recordedon the optical disk should be reproduced, in accordance with the firstdetecting signal in a valid time interval of the first detecting windowsignal, and the second detecting signal in a valid time interval of thesecond detecting window signal.

[0047] In the above-mentioned apparatus, the first area detectingcircuit preferably comprises a first comparator for comparing thereproduced signal from the optical disk upon reproducing informationrecorded in the first area, with a predetermined first threshold value,and outputting a first comparison result signal.

[0048] In the above-mentioned apparatus, the second area detectingcircuit preferably comprises:

[0049] a second comparator for comparing the reproduced signal from theoptical disk upon reproducing information recorded in the second area,with a predetermined second threshold value, and outputting a secondcomparison result signal;

[0050] a third comparator for comparing the reproduced signal from theoptical disk upon reproducing information recorded in the second area,with a predetermined third threshold value, and outputting a thirdcomparison result signal; and

[0051] an arithmetic logic circuit for performing a logic operationbetween the second comparison result signal and the third comparisonresult signal, and outputting a logic operation result signal.

[0052] In the above-mentioned apparatus, the first area detectingcircuit preferably detects the first area in accordance with areproduced signal from the optical disk upon reproducing informationrecorded on a track including the first area, and a reproduced signalfrom the optical disk upon reproducing information recorded on a furthertrack including the first area and adjacent to the track, and outputsthe first detecting signal.

[0053] According to a further aspect of the present invention, there isprovided a method for reproducing information recorded on an opticaldisk which is provided for recording data of a signal modulatedaccording to a predetermined modulation method in a form ofconcavo-convex pits, the optical disk comprising a first area having areflecting film partly removed, the method including the steps of:

[0054] detecting the first area in accordance with a reproduced signalfrom the optical disk upon reproducing information recorded in the firstarea, and outputting a first detecting signal; and

[0055] judging whether or not the information recorded on the opticaldisk should be reproduced, in accordance with the first detectingsignal.

[0056] In the above-mentioned method, the step of detecting the firstarea and outputting the first detecting signal preferably includes thestep of:

[0057] detecting the first area in accordance with a reproduced signalfrom the optical disk upon reproducing information recorded on a trackincluding the first area, and a reproduced signal from the optical diskupon reproducing information recorded on a further track including thefirst area and adjacent to the track, and outputting the first detectingsignal.

[0058] In the above-mentioned method, the step of detecting the firstarea and outputting the first detecting signal preferably includes thestep of:

[0059] judging whether or not the first area is detected in accordancewith whether or not a first number of data from a predetermined sectoraddress to the detected first area, which is counted based on thereproduced signal from the optical disk upon reproducing informationrecorded on the track including the first area, substantially coincideswith a second number of data from the sector address to the detectedfirst area, which is counted based on the reproduced signal from theoptical disk upon reproducing information recorded on a further trackincluding the first area and adjacent to the track.

[0060] According to a still further aspect of the present invention,there is provided an apparatus for reproducing information recorded onan optical disk which is provided for recording data of a signalmodulated according to a predetermined modulation method in a form ofconcavo-convex pits, the optical disk comprising a first area having areflecting film partly removed, the apparatus comprising:

[0061] detecting means for detecting the first area in accordance with areproduced signal from the optical disk upon reproducing informationrecorded in the first area, and outputting a first detecting signal; and

[0062] judging means for judging whether or not the information recordedon the optical disk should be reproduced, in accordance with the firstdetecting signal.

[0063] In the above-mentioned apparatus, the detecting means preferablydetects the first area in accordance with a reproduced signal from theoptical disk upon reproducing information recorded on a track includingthe first area, and a reproduced signal from the optical disk uponreproducing information recorded on a further track including the firstarea and adjacent to the track, and outputs the first detecting signal.

[0064] In the above-mentioned apparatus, the detecting means preferablyjudges whether or not the first area is detected in accordance withwhether or not a first number of data from a predetermined sectoraddress to the detected first area, which is counted based on thereproduced signal from the optical disk upon reproducing informationrecorded on the track including the first area, substantially coincideswith a second number of data from the sector address and the detectedfirst area, which is counted based on the reproduced signal from theoptical disk upon reproducing information recorded on a further trackincluding the first area and adjacent to the track.

BRIEF DESCRIPTION OF THE DRAWINGS

[0065] These and other objects and features of the present inventionwill become clear from the following description taken in conjunctionwith the preferred embodiments thereof with reference to theaccompanying drawings throughout which like parts are designated by likereference numerals, and in which:

[0066]FIG. 1 is a plan view showing a planar structure of an opticaldisk 1 according to a first preferred embodiment of the invention;

[0067]FIG. 2 is a sectional view showing a sectional structure of theoptical disk 1 shown in FIG. 1;

[0068]FIG. 3 is a sectional view showing a sectional structure of afirst area 2 of the optical disk 1 shown in FIG. 1;

[0069]FIG. 4 is an enlarged view showing a second area 3 of the opticaldisk 1 shown in FIG. 1 and a plan view showing a planar structure of along pit 107;

[0070]FIG. 5 is a sectional view and a block diagram showing a method offorming a non-reflecting portion 106 of the optical disk 1 shown in FIG.1;

[0071]FIGS. 6A, 6B and 6C show signal waveforms of reproduced signalswhich are obtained during reproduction of information in an area of thenon-reflecting portion 106 of the optical disk 1 shown in FIG. 1, inwhich the signal waveforms are proportional to the intensity ofreflected light relative to a circumferential length, wherein FIG. 6A isa waveform chart of the signal waveform of the reproduced signal at alow degree of modulation, FIG. 6B is a waveform chart of the signalwaveform of the reproduced signal at a high degree of modulation, andFIG. 6C is a waveform chart of the signal waveform of the reproducedsignal at a high degree of modulation and in a defocus state;

[0072]FIG. 7 is a block diagram showing a configuration of a first areadetecting circuit 23 a for use in the first preferred embodiment of theinvention;

[0073]FIG. 8 is a plan view showing a planar structure of the long pit107 formed in the second area 3 of the optical disk 1 shown in FIG. 1;

[0074]FIGS. 9A and 9B show a sectional structure of the long pit 107shown in FIG. 8, wherein FIG. 9A is a sectional view taken along theline A-A′ of FIG. 8 located in the center of the long pit 107, and FIG.9B is a sectional view taken along the line B-B′ of FIG. 8 located in anend portion of the long pit 107;

[0075]FIG. 10 is a block diagram showing a configuration of a secondarea detecting circuit 24 a for use in the first preferred embodiment ofthe invention;

[0076]FIGS. 11A, 11B and 11C show a method of detecting the second areaby the second area detecting circuit 24 a shown in FIG. 10, wherein FIG.11A is a waveform chart of a signal waveform of a reproduced signal inan area including the area of the long pit 107, FIG. 11B is a waveformchart of a signal waveform of an output signal CV1 from a comparator 8shown in FIG. 10, which uses a first threshold value voltage V1th, andFIG. 11C is a waveform chart of a signal waveform of an output signalCV2 from a comparator 9 shown in FIG. 10, which uses a second thresholdvalue voltage V2th;

[0077]FIG. 12 shows a table of waveform charts of signal waveforms ofreproduced signals which are obtained during reproduction of informationin the area of the non-reflecting portion 106 and the area of the longpit 107 on each optical disk, where FIG. 12(a) shows waveform charts ofthe signal waveforms of the reproduced signals which are obtained duringreproduction of information in the area of the non-reflecting portion106 and the area of the long pit 107 on the authorized optical disk 1according to the first preferred embodiment of the invention, FIG. 12(b)shows waveform charts of the signal waveforms of the reproduced signalswhich are obtained during reproduction of information in the area of thenon-reflecting portion 106 and the area of the long pit 107 on a firstpirated optical disk, and FIG. 12(c) shows waveform charts of the signalwaveforms of the reproduced signals which are obtained duringreproduction of information in the area of the non-reflecting portion106 and the area of the long pit 107 on a second pirated optical disk;

[0078]FIG. 13 is a plan view showing a planar structure of an opticaldisk 1 a according to a second preferred embodiment of the invention;

[0079]FIG. 14 is a block diagram showing a configuration of a first areadetecting circuit 23 for use in the second preferred embodiment of theinvention;

[0080]FIG. 15 is a block diagram showing a configuration of a secondarea detecting circuit 24 for use in the second preferred embodiment ofthe invention;

[0081]FIG. 16 is a block diagram showing a configuration of an opticaldisk reproducing apparatus for use in a third preferred embodiment ofthe invention;

[0082]FIG. 17 shows a method of detecting the first area 2 for use inthe optical disk reproducing apparatus shown in FIG. 16 and is anenlarged plan view showing the correlation from each track on theoptical disk 1 in a circumferential direction to the first area 2;

[0083]FIG. 18 is a flow chart of a first portion of processing fordetecting and judging the first area to be executed by a systemcontroller 25 shown in FIG. 16; and

[0084]FIG. 19 is a flow chart of a second portion of the processing fordetecting and judging the first area to be executed by the systemcontroller 25 shown in FIG. 16.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0085] An optical disk, an optical disk reproducing method and anoptical disk reproducing apparatus according to preferred embodiments ofthe invention will be described below with reference to the accompanyingdrawings. Herein, optical disks include an optical disk and amagneto-optical disk such as a CD, a video CD, a CD-ROM, a CD-R, aCD-RW, an MD, a DVD, a DVD-ROM, a DVD-RAM and a DVD-RW.

[0086] First Preferred Embodiment

[0087]FIG. 1 is a plan view showing a planar structure of an opticaldisk 1 according to a first preferred embodiment of the invention, FIG.2 is a sectional view showing a sectional structure of the optical disk1 shown in FIG. 1, FIG. 3 is a sectional view showing a sectionalstructure of a first area 2 of the optical disk 1 shown in FIG. 1, andFIG. 4 is an enlarged view showing a second area 3 of the optical disk 1shown in FIG. 1 and a plan view showing a planar structure of a long pit107.

[0088]FIG. 1 shows a planar structure of an information recording areaof the overall optical disk 1. The information recording area comprisesa lead-in area 111 for recording control information, a data recordingarea 112 that is a user data recording area for recording contentinformation composed of content control information and content data,and a lead-out area 113. The optical disk 1 has a rotation driving hole1 h in the center thereof. The lead-in area 111, the data recording area112 and the lead-out area 113 are located in an order from the inside ofthe optical disk 1 toward the outside thereof. In the data recordingarea 112, the first area 2, which will be described later in detail,extends so as to have a longitudinal direction in a radial direction ofthe optical disk 1, while the second area 3, which will be describedlater in detail, extends so as to have a longitudinal direction in acircumferential direction of the optical disk 1.

[0089] As shown in FIG. 2, the optical disk 1 is formed of a bondedstructure of a transparent optical disk substrate 100 and an opticaldisk substrate 102. A reflecting film 101 of a material such as aluminumor gold is formed, by using the sputtering method which has been alreadyknown to those skilled in the art, on one surface of the transparentoptical disk substrate 100 which is formed so that concavo-convex pitsare formed thereon based on a replica. Then, one surface of the opticaldisk substrate 102 made through another step is bonded onto the surfaceof the transparent optical disk substrate 100 on which the reflectingfilm 101 is formed, using an adhesive layer 103 made of anultraviolet-curing resin which is located between the two optical disksubstrates 100 and 102. After that, the bonded optical disk substrates100 and 102 are irradiated with ultraviolet rays, and this leads to theadhesive layer 103 being allowed to cure and thus the two optical disksubstrates 100 and 102 are firmly bonded to each other. As a result, theoptical disk 1 is made.

[0090]FIG. 3 shows a sectional structure of the first area 2 having anon-reflecting portion 106 formed by partly removing the reflecting film101 in the optical disk 1 shown in FIG. 1. A method of making thenon-reflecting portion 106 is disclosed in International Publication No.WO96/16401. With reference to the publication, the method of making thenon-reflecting portion 106 will be briefly described with reference toFIG. 5. The optical disk 1 completed by the method described above withreference to FIG. 2 is irradiated on the side of the transparent opticaldisk substrate 100 with pulse laser light emitted from a YAG pulse laser104 so that the pulse laser light is focused on the reflecting film 101by a condenser lens 105. Thus, the reflecting film 101 is partlyremoved. As a consequence, the non-reflecting portion 106 is formed inthe first area 2.

[0091]FIGS. 6A to 6C show signal waveforms of reproduced signals whichare obtained during reproduction of information in an area of thenon-reflecting portion 106 of the optical disk 1 shown in FIG. 1. Inthis case, the signal waveforms are proportional to the intensity ofreflected light relative to a circumferential length. FIG. 6A is awaveform chart of the signal waveform of the reproduced signal at a lowdegree of modulation, FIG. 6B is a waveform chart of the signal waveformof the reproduced signal at a high degree of modulation, and FIG. 6C isa waveform chart of the signal waveform of the reproduced signal at ahigh degree of modulation and in a defocus state.

[0092] When information recorded in the first area 2 of the optical disk1 configured as described above with reference to FIG. 5 is reproducedby using the optical disk reproducing apparatus, there are obtained thesignal waveforms of the reproduced signals including RF signals changingperiodically as shown in FIGS. 6A to 6C. At a low degree of modulation,a dark level of the periodic RF signal does not drop sufficiently. Inthis case, the dark level refers to the darkest level of an envelope ofthe RF signal, and is called an envelope bottom level. Therefore, asshown in FIG. 6A, the level of the reproduced signal in the area of thenon-reflecting portion 106 is compared with a threshold value, namely, afirst slice level that is lower than the envelope bottom level of the RFsignal by a predetermined amount of level shift, and then, the presenceof the non-reflecting portion 106 can be detected.

[0093] At a high degree of modulation, as shown in FIG. 6B, the envelopebottom level of the RF signal drops sufficiently. Thus, little or nodifference is made between the envelope bottom level of the RF signaland an output level of the non-reflecting portion 106. Therefore, it isnot easy to detect the non-reflecting portion 106. However, in thiscase, an optical head, i.e., an optical pickup of the optical diskreproducing apparatus is controlled so that a spot of the laser light tobe applied to the optical disk 1 becomes in a defocus state. Thus, theenvelope bottom level of the reproduced RF signal rises, and therefore,a significant difference is made between the envelope bottom level ofthe RF signal and the level of the reproduced signal in the area of thenon-reflecting portion 106. Consequently, the area of the non-reflectingportion 106 can be easily detected. In actual, when an attempt is madeto make the spot of the laser light on the optical disk 1 be in adefocus state and to reproduce information recorded on the optical disk1, a reproduced clock signal, which is to be generated from thereproduced signal by a PLL circuit in an analog processor, cannot be, insome cases, generated. Therefore, in some cases, the PLL circuit is heldimmediately before the spot of the laser light is made in a defocusstate, and the analog processor is controlled so as to hold andreproduce the reproduced clock signal in a state immediately before thedefocus state.

[0094] Furthermore, it may be a possible method to reproduce informationrecorded in the first area 2 by performing tracking an area locatedbetween two adjacent tracks on the optical disk 1. In this case, in amanner similar to above, the envelope bottom level, i.e., the dark levelof the RF signal rises in any area other than the non-reflecting portion106, however, the reproduced clock signal cannot be generated due tocross-talk between the RF signals. Thus, a reproduced clock immediatelybefore tracking between the tracks is held and reproduced in a stateimmediately before tracking.

[0095]FIG. 7 is a block diagram showing a configuration of a first areadetecting circuit 23 a for use in the first preferred embodiment of theinvention. The first area detecting circuit 23 a comprises a data slicer4, an envelope bottom detecting circuit 5, a level shift circuit 6, anda comparator 7.

[0096] Referring to FIG. 7, the reproduced signal outputted from ananalog processor 20 of FIG. 16 for applying analog signal processing tothe reproduced signal from the optical disk 1 is inputted to the dataslicer 4, a first input terminal of the comparator 7 and the envelopebottom detecting circuit 5. The data slicer 4 binarizes the reproducedsignal, which is inputted from the optical disk 1 through the analogprocessor 20, by using a predetermined threshold value. Thus, the dataslicer 4 converts the reproduced signal into digital data, i.e., abinarized reproduced signal, and then, outputs the binarized reproducedsignal. On the other hand, the envelope bottom detecting circuit 5detects the envelope bottom level that is the lowest level of theenvelope of the input reproduced signal, and then, outputs a lowenvelope signal having the detected envelope bottom level to the levelshift circuit 6. Subsequently, the level shift circuit 6 shifts downwardthe envelope bottom level of the input low envelope signal by apredetermined amount of level shift (See FIGS. 6A and 6C), and then,outputs a threshold value signal having the above-mentionedlevel-shifted first slice level to a second input terminal of thecomparator 7. Furthermore, the comparator 7 compares the reproducedsignal inputted to the first input terminal with the threshold valuesignal having the first slice level inputted to the second inputterminal. When the level of the reproduced signal is lower than thefirst slice level, i.e., in the area of the non-reflecting portion 106,the comparator 7 outputs a low-level signal as a non-reflecting portiondetecting signal. In the above-mentioned manner, the area of thenon-reflecting portion 106 in the first area 2 having the reflectingfilm partly removed can be easily detected.

[0097] Next, description will be made with regard to the second area 3having a concavo-convex long pit 107 having a length longer than amaximum pit length determined by a predetermined modulation method,i.e., having a length which is different from concavo-convex pitssatisfying the above-mentioned modulation method. As shown in the planarstructures of FIGS. 4 and 8, the long pit 107 having a length equivalentto about 100T in the longitudinal direction parallel to thecircumferential direction is formed in the second area 3, for example,provided that a pit length for generally recording user data in the datarecording area 112 is 3T to 14T (where T denotes a length correspondingto one reproduced clock signal). FIGS. 9A and 9B show a sectionalstructure of the long pit 107 shown in FIG. 8. FIG. 9A is a sectionalview taken along the line A-A′ of FIG. 8 located in the center of thelong pit 107. FIG. 9B is a sectional view taken along the line B-B′ ofFIG. 8 located in an end portion of the long pit 107.

[0098] As shown in FIGS. 9A and 9B, the long pit 107 has a sectionalstructure in which the curvature of each edge of a cross section of thelong pit 107 is larger at the position closer to the circumferential,i.e., longitudinal center (referring to a portion located at themidpoint position between both end portions in the longitudinaldirection). The cross section in the center of the long pit 107 has asectional shape shown in FIG. 9A. The cross sections in both the endportions of the long pit 107 have a sectional shape shown in FIG. 9B.The long pit 107 having the above-mentioned sectional shape can beeasily formed by appropriately setting conditions for forming thetransparent optical disk substrate 100 of the optical disk 1, as wellknown.

[0099]FIG. 11A shows a signal waveform of a reproduced signal which isobtained when information recorded in the second area 3 is reproduced inthe circumferential direction. The horizontal axis shown in FIGS. 11A,11B and 11C represents the elapsed time corresponding to thecircumferential length when information recorded in the second area 3 isreproduced in the circumferential direction by moving the spot of thelaser light to be applied to the optical disk 1 at a constant speed.

[0100] As shown in FIG. 11A, as the spot of the laser light to beapplied to the optical disk 1 is moved from one end of the long pit 107to the longitudinal center of the long pit 107 in the circumferentialdirection, the level of the reproduced signal rises toward a brightlevel with a gradual gradient, and then, the level of the reproducedsignal reaches the brightest level in the area of the long pit 107 inthe longitudinal center of the long pit 107. Furthermore, as the spot ofthe laser light to be applied to the optical disk 1 is moved from thecenter of the long pit 107 to the other end of the long pit 107 in thecircumferential direction, the level of the reproduced signal dropstoward the dark level with a gradual gradient. The level of thereproduced signal changes in the area of the long pit 107 as mentionedabove for the following reason. As shown in FIG. 9A, the curvature ofthe edge of the long pit 107 in which interference occurs is larger inthe center of the long pit 107, thus a substantial pit depth D is notequal to a specified value, i.e., λ/4 (where λ denotes an averagewavelength of the laser light from an optical head 18), and, therefore,the level of the reproduced signal rises to the bright level.

[0101] Next, a method of identifying the second area 3 will be describedwith reference to FIGS. 10, 11A, 11B and 11C. FIG. 10 is a block diagramshowing a configuration of a second area detecting circuit 24 a for usein the first preferred embodiment of the invention. FIGS. 11A to 11Cshow a method of detecting the second area by the second area detectingcircuit 24 a shown in FIG. 10. FIG. 11A is a waveform chart of a signalwaveform of a reproduced signal in an area including the area of thelong pit 107. FIG. 11B is a waveform chart of a signal waveform of anoutput signal CV1 from a comparator 8 shown in FIG. 10, which uses afirst threshold value voltage V1th close to the bright level. FIG. 11Cis a waveform chart of a signal waveform of an output signal CV2 from acomparator 9 shown in FIG. 10, which uses a second threshold valuevoltage V2th close to the dark level.

[0102] Referring to FIG. 10, the second area detecting circuit 24 acomprises the data slicer 4, the two comparators 8 and 9, two thresholdvalue voltage generators 8 a and 9 a, two counters 10 and 11, and anormal length pit discriminating circuit 12. In FIG. 10, the samecomponents as the components shown in FIG. 7 are indicated by the samereference numerals.

[0103] Referring again to FIG. 10, the reproduced signal outputted fromthe analog processor 20 of FIG. 16 for applying analog signal processingto the reproduced signal from the optical disk 1 is inputted to the dataslicer 4 and the respective first input terminals of the two comparators8 and 9. The data slicer 4 binarizes the reproduced signal, which isinputted from the optical disk 1 through the analog processor 20, byusing a predetermined threshold value. Thus, the data slicer 4 convertsthe reproduced signal into digital data, i.e., a binarized reproducedsignal, and then, outputs the binarized reproduced signal. On the otherhand, the first threshold value voltage V1th from the threshold valuevoltage generator 8 a is inputted to a second input terminal of thecomparator 8. The comparator 8 compares the reproduced signal inputtedto the first input terminal to the first threshold value voltage V1thclose to the bright level, and then, outputs a comparison result signalto the counter 10. When the level of the reproduced signal is equal toor higher than the first threshold value voltage V1th, the comparator 8outputs a high-level comparison result signal. In the other cases, thecomparator 8 outputs a low-level comparison result signal. Moreover, thesecond threshold value voltage V2th from the threshold value voltagegenerator 9 a is inputted to a second input terminal of the comparator9. The comparator 9 compares the reproduced signal inputted to the firstinput terminal with the second threshold value voltage V2th close to thedark level, and then, outputs a comparison result signal to the counter11. When the level of the reproduced signal is equal to or higher thanthe second threshold value voltage V2th, the comparator 9 outputs ahigh-level comparison result signal. In the other cases, the comparator9 outputs a low-level comparison result signal.

[0104] Each of the counters 10 and 11 counts channel bit clock signalspck which are reproduced from the reproduced signals by the analogprocessor 20, during a valid time interval during which the inputcomparison result signal is at high level. Then, each of the counters 10and 11 outputs time data of a count result (corresponding to the timeinterval T1 shown in FIG. 11B and the time interval T2 shown in FIG. 11Cduring which the comparison result signal is at high level) to thenormal length pit discriminating circuit 12. Subsequently, when the timeinterval T2 shown in FIG. 11C is equal to or longer than a predeterminedfirst threshold time and the time interval between the start of the timeinterval T2 (the leading edge of a pulse of the high-level comparisonresult signal in the time interval T2 in the area of the long pit 107)and the start of the time interval T1 (the leading edge of a pulse ofthe high-level comparison result signal in the time interval T1 in thearea of the long pit 107) is equal to or longer than a predeterminedsecond threshold time, the normal length pit discriminating circuit 12judges that the presence of the long pit 107, i.e., the presence of thesecond area 3 is detected, and then, the circuit 12 outputs a long pitdetecting signal.

[0105] In the case of a typical normal pit, in a form of which data of asignal modulated according to using a predetermined modulation method isrecorded on the optical disk 1, the reproduced level of the normal pitabruptly or suddenly changes from the dark level to the bright level,and the time interval for the change is substantially fixed. However,the reproduced level of the above-mentioned long pit 107 graduallychanges from the dark level to the bright level with a more gradualgradient than the gradient of change in the typical normal pit.Therefore, the long pit 107 or the second area 3 can be easily detectedby using the above-described method, i.e., by using the second areadetecting circuit 24 a shown in FIG. 10.

[0106] Description will be made with regard to the case in which apirate makes a so-called RF copy of the optical disk 1 as configured asdescribed above. “RF copying” described herein refers to making a copyof the optical disk is made by using a stamper made by the use of an RFsignal that is a reproduced signal from the optical disk 1.

[0107] Description will be made with reference to FIG. 12 with regard tothe case in which the optical disk 1 is made as mentioned above. FIG. 12shows a table of waveform charts of signal waveforms of reproducedsignals which are obtained during reproduction of information in thearea of the non-reflecting portion 106 and the area of the long pit 107on each optical disk. FIG. 12(a) shows waveform charts of the signalwaveforms of the reproduced signals which are obtained duringreproduction of information in the area of the non-reflecting portion106 and the area of the long pit 107 on the authorized optical disk 1according to the first preferred embodiment of the invention. FIG. 12(b)shows waveform charts of the signal waveforms of the reproduced signalswhich are obtained during reproduction of information in the area of thenon-reflecting portion 106 and the area of the long pit 107 on a firstpirated optical disk made by RF copying. FIG. 12(c) shows waveformcharts of the signal waveforms of the reproduced signals which areobtained during reproduction of information in the area of thenon-reflecting portion 106 and the area of the long pit 107 on a secondpirated optical disk made under changed conditions from forming thefirst pirated optical disk.

[0108] In general, the non-reflecting portion 106 of the pirated opticaldisk, which is made by making a RF copy of the reproduced signal of thenon-reflecting portion 106 as it is, is recorded as the long pit. Thelong pit 107 of the authorized optical disk is judged as the presence orabsence of the pit, and thus the long pit 107 of the pirated opticaldisk is recorded as if the length of the long pit 107 were reduced.

[0109] Therefore, as shown in FIG. 12, when information recorded on thepirated optical disk is reproduced, the RF signal contains a long-timedark level signal in an area corresponding to the first area 2 of theauthorized optical disk, and thus, it seems as if the long pit 107 wereformed in the above-mentioned area. However, the signal waveform of thereproduced signal that settles at the dark level and is continuous (Seea column of the area of the non-reflecting portion 106 shown in FIG.12(b)), or the signal waveform of the reproduced signal similar to thereproduced signal of the second area 3 of the authorized optical disk(See a column of the area of the non-reflecting portion 106 shown inFIG. 12(c)) is obtained in accordance with the forming conditions.

[0110] Information recorded in a portion corresponding to the secondarea 3 of the authorized optical disk is reproduced as a long brightlevel sandwiched between short dark levels. When a pirated, unauthorizedoptical disk is copied by using the stamper made by the use of the RFsignal, a pit shorter than the normal long pit 107 is recorded.Moreover, the reproduced level of the shorter pit changes from the darklevel to the bright level more abruptly or suddenly than the long pit107 of the authorized optical disk (See a column of the area of the longpit 107 shown in FIG. 12(b) and FIG. 12(c)). As described above, it isjudged whether or not the optical disk is the authorized optical disk 1in accordance with a combination of the reproduced signal of thenon-reflecting portion 106 and the reproduced signal of the long pit107. Thus, it can be judged whether or not information recorded on theoptical disk 1 is reproduced.

[0111] As described above, according to the preferred embodiment, theoptical disk, which is used for recording data of a signal modulatedaccording to a predetermined modulation method in a form ofconcavo-convex pits, comprises the first area 2 having the reflectingfilm partly removed, and the second area 3 for recording pits which aredifferent from pits satisfying the requirements of the predeterminedmodulation method. Thus, the pirated optical disk is easily identified,and it can be judged whether or not information recorded on the opticaldisk is reproduced. Therefore, the optical disk 1 capable of protectingthe right of a copyright owner can be provided.

[0112] Second Preferred Embodiment

[0113]FIG. 13 is a plan view showing a planar structure of an opticaldisk 1 a according to a second preferred embodiment of the invention.The optical disk 1 a according to the second preferred embodiment ischaracterized by that the optical disk 1 according to the firstpreferred embodiment has a recording area called a BCA (Burst CuttingArea) 13 in which location information of the first area is stored in afirst area location information recording area 13 a and locationinformation of the second area is stored in a second area locationinformation recording area 13 b. The other structure of the optical disk1 a is the same as those of the optical disk 1 according to the firstpreferred embodiment. When information recorded on the optical disk 1 aaccording to the second preferred embodiment is reproduced, whether ornot the optical disk is the authorized optical disk 1 a is more easilyjudged in accordance with die location information recorded in the firstarea location information recording area 13 a and the second arealocation information recording area 13 b in the BCA 13.

[0114]FIG. 14 is a block diagram showing a configuration of a first areadetecting circuit 23 for use in the second preferred embodiment of theinvention. In FIG. 14, the same components as the components of thefirst area detecting circuit 23 a shown in FIG. 7 are indicated by thesame reference numerals, and the detailed description thereof isomitted. In the present preferred embodiment, an address of thenon-reflecting portion 106 and an address of the long pit 107 arewritten in the BCA 13, and each of the addresses contains locationinformation composed of an ID number and the number of clocks.

[0115] Referring to FIG. 14, the first area detecting circuit 23comprises a window generating circuit 14, a counter 15, a latch 16, aBCA reproducing circuit 31 and an AND gate 32, in addition to the dataslicer 4, the envelope bottom detecting circuit 5, the level shiftcircuit 6 and the comparator 7.

[0116] The BCA reproducing circuit 31 reproduces information datarecorded in the BCA 13 of the optical disk 1 a, in particular,reproduces the address of the location information composed of the IDnumber and the number of clocks, and outputs the reproduced informationdata to the window generating circuit 14. Then, the window generatingcircuit 14 generates a window signal for detecting the non-reflectingportion 106 in accordance with the location information that is recordedin the BCA 13 and reproduced from the BCA 13 by the BCA reproducingcircuit 31, and the circuit 14 outputs the window signal to a secondinput terminal of the AND gate 32. In other words, the window generatingcircuit 14 compares the address contained in the reproduced signal withthe address of the location information in accordance with thereproduced signal outputted from the analog processor 20 and thelocation information from the BCA reproducing circuit 31. When theseaddresses coincide with each other, the window generating circuit 14outputs a high-level window signal, and thus, enables a window. Whenthese addresses does not coincide with each other, the window generatingcircuit 14 outputs a low-level window signal, and thus, disables thewindow. After the count of the counter 15 is reset to zero in accordancewith a reset signal from the analog processor 20, the counter 15 countsthe channel bit clock signals pck, i.e., the reproduced clocks that aregenerated from the reproduced signals by the analog processor 20, andthe counter 15 outputs count data to the latch 16. The count dataindicates circumferential location information since the instant whenthe count is reset in accordance with the reset signal.

[0117] The non-reflecting portion detecting signal from the comparator 7is inputted to a first input terminal of the AND gate 32. The AND gate32 outputs a high-level signal to the latch 16 only when both of twoinput signals are at high level. Therefore, the AND gate 32 outputs thehigh-level signal to the latch 16, when the non-reflecting portion 106is detected by the comparator 7 and the location information from theBCA 13 coincides with the location information of the reproduced signal.In response to the high-level signal, the latch 16 latches the countdata outputted from the counter 15 by the use of the non-reflectingportion detecting signal obtained during the valid time interval of thewindow generated by the window generating circuit 14, and then, thelatch 16 outputs correct detected location information.

[0118]FIG. 15 is a block diagram showing a configuration of a secondarea detecting circuit 24 for use in the second preferred embodiment ofthe invention. In FIG. 15, the same components as the components of thesecond area detecting circuit 24 a shown in FIGS. 14 and 10 areindicated by the same reference numerals.

[0119] The second area detecting circuit 24 according to the secondpreferred embodiment is characterized by the second area detectingcircuit 24 further comprising the BCA reproducing circuit 31 and thewindow generating circuit 14, in addition to the data slicer 4, the twocomparators 8 and 9, the two threshold value voltage generators 8 a and9 a, the two counters 10 and 11, and the normal length pitdiscriminating circuit 12.

[0120] Referring to FIG. 15, in a manner similar to that of the BCAreproducing circuit 31 and the window generating circuit 14 shown inFIG. 14, the window generating circuit 14 generates a window signal fordetecting the long pit 107 in accordance with the location informationreproduced from the BCA 13 by the BCA reproducing circuit 31, and thecircuit 14 outputs the window signal to each of the counters 10 and 11.Only when a high-level window signal is inputted to each of the counters10 and 11, the window generating circuit 14 opens the window, and causesthe counters 10 and 11 to operate only during the time interval of thewindow, and then, the normal length pit discriminating circuit 12 judgesthe presence or absence of the long pit 107.

[0121] Furthermore, a method of identifying the authorized optical disk1 a by using the first area detecting circuit 23 shown in FIG. 14, andthe second area detecting circuit 24 shown in FIG. 15 will be described.

[0122] First of all, before reproducing the content information recordedon the optical disk 1 a, the location information recorded in the BCA 13is read out by using the BCA reproducing circuit 31. Then, the opticalhead 18 shown in FIG. 16 is allowed to perform a seek in accordance withthe location information, thereby reproducing information recorded inthe first area 2. A method of detecting the non-reflecting portion 106from the reproduced signal is the same as the method of the firstpreferred embodiment, and thus, the description thereof is omitted. Theintensity of copyright protection further improves because of theaddition of judgment about the presence or absence of the long pit 107in the location recorded in the location information. Furthermore, thelocation information recorded in the BCA 13 is read out by using the BCAreproducing circuit 31. Then, the optical head 18 shown in FIG. 16 isallowed to perform seeks in accordance with the location information,thereby reproducing information recorded in the second area 3. Then, thelegality of the long pit 107 is judged in accordance with the reproducedsignal. Whether or not the optical disk 1 a is authorized is judged inaccordance with detected signals from the reproduced signals of thefirst area 2 and the second area 3. Thus, there can be judged whether ornot information recorded on the optical disk 1 a is reproduced. Thus,the so-called RF copy can be prevented, and therefore, a copyright canbe more solidly or certainly protected.

[0123] In the present preferred embodiment, the location informationrecorded in the area 13 a for recording the location information of thefirst area 2 and the area 13 b for recording the location information ofthe second area 3 contains the address, for example. Specifically, asshown in FIGS. 14 and 15, the location information can be specified bythe address of the ID number or the like, and the number of clocks ofthe channel bit clock signals pck from a sector header to a detectedsector. The location information recorded in the area 13 a for recordingthe location information of the first area 2 and the area 13 b forrecording the location information of the second area 3 is not limitedto this, and may be any other type of location information capable ofspecifying the respective locations of the non-reflecting portion 106and the long pit 107.

[0124] As described above, according to the present preferredembodiment, the optical disk 1 a, which is provided for recording dataof a signal modulated according to a predetermined modulation method ina form of concavo-convex pits, comprises the first area 2 having thenon-reflecting portion 106 formed by partly removing the reflectingfilm, and the second area 3 for recording the long pit 107 which isdifferent from pits satisfying the requirements of the predeterminedmodulation method. Moreover, for example, the BCA 13 includes the firstarea location information recording area 13 a for recording the locationinformation of the first area 2 on the optical disk 1 a, and the secondarea location information recording area 13 b for recording the locationinformation of the second area 3 on the optical disk 1 a. Thenon-reflecting portion 106 formed in the first area 2 and the long pit107 formed in the second area 3 are identified by specifying therespective positions of the areas 2 and 3 in accordance with thelocation information recorded in the first area location informationrecording area 13 a and the second area location information recordingarea 13 b. Thus, the authorized optical disk 1 a is more easilyidentified at high speed. Therefore, there can be judged whether or notinformation recorded on the optical disk 1 a is reproduced.

[0125] Third Preferred Embodiment

[0126]FIG. 16 is a block diagram showing a configuration of an opticaldisk reproducing apparatus for use in a third preferred embodiment ofthe invention. The optical disk reproducing apparatus according to thethird preferred embodiment comprises the optical head 18, a headamplifier 19, the analog processor 20, an optical disk controller 21, aservo control circuit 22, the first area detecting circuit 23, thesecond area detecting circuit 24, a system controller 25, and aprocessing memory 40. In FIG. 16, the optical disk 1 may be replacedwith the optical disk 1 a according to the second preferred embodiment.

[0127] Referring to FIG. 16, a spindle motor 17 rotates the optical disk1 at a predetermined number of revolutions. The optical head 18 includesa laser diode and a photo-detector, and comprises the so-called opticalpickup. A signal reproduced by the optical head 18 is inputted to theanalog processor 20 through the head amplifier 19 for amplifying thesignal. The analog processor 20 has facilities for AGC, equalizing, dataslice, PLL and so on. The analog processor 20 applies predeterminedanalog processing to the input analog reproduced signal, and outputs theprocessed analog signal to the optical disk controller 21, the firstarea detecting circuit 23 and the second area detecting circuit 24.Furthermore, the optical disk controller 21 demodulates the reproducedsignal data, and applies error correction or the like to the data.Furthermore, the servo control circuit 22 controls the spindle motor 17and the optical head 18, thereby servo-controlling focusing, trackingand the like.

[0128] The first area detecting circuit 23 comprises the circuitaccording to the second preferred embodiment shown in FIG. 14, forexample. In accordance with the reproduced signal outputted from theanalog processor 20, the first area detecting circuit 23 detects thefirst area 2 having the non-reflecting portion 106 formed by partlyremoving the reflecting film, and then, the circuit 23 outputs thedetected location information. The first area detecting circuit 23 maybe replaced with the first area detecting circuit 23 a according to thefirst preferred embodiment shown in FIG. 7. The second area detectingcircuit 24 comprises the circuit according to the second preferredembodiment shown in FIG. 15, for example. In accordance with thereproduced signal outputted from the analog processor 20, the secondarea detecting circuit 24 detects the second area 3 having the long pit107 which is different from pits satisfying requirements of apredetermined modulation method, and has a length not satisfying anyrequirement of the above-mentioned modulation method. Then, the circuit24 outputs the long pit detecting signal. The second area detectingcircuit 24 may be replaced with the second area detecting circuit 24 aaccording to the first preferred embodiment shown in FIG. 10. The systemcontroller 25 is a controller for controlling operation of the wholeoptical disk reproducing apparatus shown in FIG. 16 by using theprocessing memory 40.

[0129] An operation of the optical disk reproducing apparatus configuredas described above will be described with reference to FIG. 17.

[0130]FIG. 17 shows a method of detecting the first area 2 for use inthe optical disk reproducing apparatus shown in FIG. 16, and is anenlarged plan view showing a correlation between each track on theoptical disk 1 in the circumferential direction and the first area 2. Inthe present preferred embodiment, it is assumed that the locationinformation of the first area 2 having the non-reflecting portion 106 ispreviously stored in the BCA 13, and that the contents of the locationinformation are composed of a sector address of a sector containing thefirst area 2 and the number of data (or the number of clocks) from thesector header to the above-mentioned detected sector. A method ofdetecting the second area 3 having the long pit 107 is the same as themethod of using the second area detecting circuit 24 according to thesecond preferred embodiment, and thus, the description thereof isomitted.

[0131]FIGS. 18 and 19 are flow charts of processing for detecting andjudging the first area to be executed by the system controller 25 shownin FIG. 16.

[0132] In step S1 of FIG. 18, first of all, the servo control circuit 22and the optical disk controller 21 are controlled so as to read out datafrom the BCA 13, and the location information of the first area 2 readout from the BCA 13 is read out and stored in the processing memory 40.Subsequently, in step S2, as shown in FIG. 17, a command for controllingthe servo control circuit 22 to seek the n-th track containing a sectoraddress ID(n) including the first area 2 is issued in accordance withthe location information stored in the processing memory 40, then thetrack containing the sector address ID(n) is sought, and informationrecorded on the sought track is reproduced. Furthermore, in step S3, itis judged whether or not the first area 2 is detected duringreproducing. Until YES is given, the processing of step S3 is repeated.When YES is given, in step S4, the first area detecting circuit 23detects detected location information containing the address of thedetected sector and the number of data from the sector header to thedetected sector, and reads in the detected location information. Then,in step S5, the detected location information detected by the first areadetecting circuit 23 is compared with the location information of thefirst area 2 previously stored in the processing memory 40. In step S6,it is judged whether or not the detected location information coincideswith the location information of the first area 2. When the detectedlocation information does not coincide with the location information ofthe first area 2 in step S6 (NO in step S6), the processing returns tostep S2, and the above-mentioned processing is repeated in order toagain detect the first area 2. On the other hand, when the detectedlocation information coincides with the location information of thefirst area 2 in step S6 (YES in step S6), in step S7, as shown in FIG.17, the servo control circuit 22 is controlled so as to trace the sametrack (the n-th track). In step S8, it is judged whether or not the samesector address ID(n) is detected. Until the same sector address ID(n) isdetected, the processing of step S8 is repeated. When the same sectoraddress ID(n) is detected in step S8, the flow goes to step S9 of FIG.19.

[0133] In step S9 of FIG. 19, the servo control circuit 22 is controlledso that the optical head 18 jumps to an adjacent next track. At thistime, at least the PLL circuit included in the analog processor 20 isheld so as to prevent the PLL circuit from tracking, since the number ofclocks is counted by the first area detecting circuit 23. In the presentpreferred embodiment, as shown in FIG. 17, whether or not the first area2 is detected on the adjacent track, namely, the (n+1)-th track by thefirst area detecting circuit 23 is similarly checked or confirmed. Thenumber of data (or the number of clocks) from the sector address ID(n)on the n-th track to the first area 2 on the n-th track detected by thefirst area detecting circuit 23 is substantially equal to the number ofdata (or the number of clocks) from the sector address ID(n) on the n-thtrack to the first area 2 on the adjacent track (detected by the firstarea detecting circuit 23). Thus, the numbers of data detected by thefirst area detecting circuit 23 must substantially coincide with eachother. When both the detected numbers of data are substantially equal toeach other, the system controller 25 judges that the detected area isthe first area 2 formed by removing the reflecting film. Specificprocessing corresponds to the processing from step S10 to step S13.

[0134] Then, in step S10, the number of data (or the number of clocks)from the sector address ID(n) on the n-th track to the first area 2 onthe n-th track is compared with the number of data (or the number ofclocks) from the sector address ID(n) on the n-th track to the firstarea 2 on the adjacent (n+1)-th track. In step S11, it is judged whetheror not the numbers of data substantially coincide with each other. Inthis case, the number of data may be counted or the number of clocks maybe counted, because data corresponding to clock signals are present. Acriterion of judgment as to whether or not the numbers of datasubstantially coincide with each other is determined in the followingmanner. Judgment is made that two types of the numbers of datasubstantially coincide with each other, as long as a difference betweenthe numbers of data is within a few clocks such as 2 or 3 clocks (or afew pieces of data). When the answer is YES in step S11, in step S12,judgment is made that the detected area is the first area 2 formed byremoving the reflecting film, and the processing for detecting andjudging the first area is ended. On the other hand, when the answer isNO in step S11, in step S13, judgment is made that the detected area isnot the first area 2, and the processing for detecting and judging thefirst area is ended.

[0135] The processing for detecting and judging the first area describedwith reference to FIGS. 18 and 19 utilizes the fact that a size of thefirst area 2 in the radial direction cannot be about the same as thesize of a track pitch and, thus, the first area 2 extends over at leasta plurality of tracks. In the present preferred embodiment, the systemcontroller 25 makes the judgment by using the result of detection of thesecond area using the second area detecting circuit 24 as mentioned inthe description of the second preferred embodiment, in addition to theprocessing for detecting and judging the first area. Thus, the systemcontroller 25 judges whether or not information recorded on the opticaldisk is reproduced. Therefore, the system controller 25 can moreaccurately judge whether or not the optical disk is the authorizedoptical disk.

[0136] As described above, the first area 2 formed by removing thereflecting film is detected based on a sector, and is further detectedbased on the number of data or the number of clocks from a predeterminedsector on an adjacent track thereof. Thus, an authorized optical diskcan be easily discriminated from, for example, a pirated copy called anRF copy made by synchronously driving a reproducing system and arecording system, because both of the systems require very strictrotation accuracy or precision.

[0137] Modified Preferred Embodiments

[0138] In the above-described preferred embodiments, the optical diskreproducing apparatus comprises the first area detecting circuit 23 or23 a and the second area detecting circuit 24 or 24 a. However, theinvention is not limited to this. The optical disk reproducing apparatusmay comprise either the first area detecting circuit or the second areadetecting circuit.

[0139] Advantages Effects of Preferred Embodiments

[0140] As described in detail above, according to the invention, anoptical disk, which is provided for recording data of a signal modulatedaccording to a predetermined modulation method in a form ofconcavo-convex pits, comprises a first area having a reflecting filmpartly removed, and a second area for recording pits which are differentfrom pits satisfying the requirements of the predetermined modulationmethod. Thus, a pirated optical disk is easily identified, and it can bejudged whether or not information recorded on the optical disk isreproduced. Therefore, the right of a copyright owner can be certainlyprotected.

[0141] Moreover, the optical disk further comprises a first arealocation information recording area recording location information ofthe first area, and a second area location information recording arearecording location information of the second area. Thus, the first areaand the second area can be specified in accordance with the locationinformation of the first area and the location information of the secondarea. Therefore, the first area and the second area can be more easilyidentified at high speed. Accordingly, the optical disk of the inventionhas a great practical merit.

[0142] Furthermore, the first area is again detected on an adjacenttrack to detect the first area formed by removing the reflecting film,and then, it is judged whether or not information recorded on theoptical disk is reproduced. Therefore, the right of a copyright ownercan be certainly protected, and measures to more solidly protect againsta pirated copy can be provided.

[0143] Although the present invention has been fully described inconnection with the preferred embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications are apparent to those skilled in the art. Such changes andmodifications are to be understood as included within the scope of thepresent invention as defined by the appended claims unless they departtherefrom.

What is claimed is:
 1. An apparatus for reproducing information recordedon an optical disk which is provided for recording data of a signalmodulated according to a predetermined modulation method in a form ofconcavo-convex pits, said optical disk comprising a first area having areflecting film partly removed, and a second area for recording pitswhich are different from pits satisfying requirements of saidpredetermined modulation method, said apparatus comprising: a first areadetecting circuit for detecting said first area in accordance with areproduced signal from said optical disk upon reproducing informationrecorded in said first area, and outputting a first detecting signal; asecond area detecting circuit for detecting said second area inaccordance with a reproduced signal from said optical disk uponreproducing information recorded in said second area, and outputting asecond detecting signal; and judging means for judging whether or notthe information recorded on said optical disk should be reproduced, inaccordance with said first and second detecting signals, wherein saidsecond area detecting circuit comprises: a second comparator forcomparing the reproduced signal from said optical disk upon reproducinginformation recorded in said second area, with a predetermined secondthreshold value, and outputting a second comparison result signal; athird comparator for comparing the reproduced signal from said opticaldisk upon reproducing information recorded in said second area, with apredetermined third threshold value, and outputting a third comparisonresult signal; and an arithmetic logic circuit for performing a logicoperation between said second comparison result signal and said thirdcomparison result signal, and outputting a logic operation resultsignal, wherein said first area detecting circuit judges whether or notsaid first area is detected in accordance with whether or not a firstnumber of data from a predetermined sector address to said detectedfirst area, which is counted based on the reproduced signal from saidoptical disk upon reproducing information recorded on the trackincluding said first area, substantially coincides with a second numberof data from said sector address to said detected first area, which iscounted based on the reproduced signal from said optical disk uponreproducing information recorded on a further track including said firstarea and adjacent to said track.
 2. An apparatus for reproducinginformation recorded on an optical disk which is provided for recordingdata of a signal modulated according to a predetermined modulationmethod in a form of concavo-convex pits, said optical disk comprising afirst area having a reflecting film partly removed, a second area forrecording pits which are different from pits satisfying requirements ofsaid predetermined modulation method, a first area location informationrecording area for recording location information of said first area onsaid disk, and a second area location information recording area forrecording location information of said second area on said disk, saidapparatus comprising: a first detecting window generating circuit forgenerating a first detecting window signal in accordance with saidlocation information of said first area on said disk recorded in saidfirst area location information recording area; a second detectingwindow generating circuit for generating a second detecting windowsignal in accordance with said location information of said second areaon said disk recorded in said second area location information recordingarea; a first area detecting circuit for detecting said first area inaccordance with a reproduced signal from said optical disk uponreproducing information recorded in said first area, and outputting afirst detecting signal; a second area detecting circuit for detectingsaid second area in accordance with a reproduced signal from saidoptical disk upon reproducing information recorded in said second area,and outputting a second detecting signal; and judging means for judgingwhether or not the information recorded on said optical disk should bereproduced, in accordance with said first detecting signal in a validtime interval of said first detecting window signal, and said seconddetecting signal in a valid time interval of said second detectingwindow signal, wherein said second area detecting circuit comprises: asecond comparator for comparing the reproduced signal from said opticaldisk upon reproducing information recorded in said second area, with apredetermined second threshold value, and outputting a second comparisonresult signal; a third comparator for comparing the reproduced signalfrom said optical disk upon reproducing information recorded in saidsecond area, with a predetermined third threshold value, and outputtinga third comparison result signal; and an arithmetic logic circuit forperforming a logic operation between said second comparison resultsignal and said third comparison result signal, and outputting a logicoperation result signal, wherein said first area detecting circuitjudges whether or not said first area is detected in accordance withwhether or not a first number of data from a predetermined sectoraddress to said detected first area, which is counted based on thereproduced signal from said optical disk upon reproducing informationrecorded on the track including said first area, substantially coincideswith a second number of data from said sector address to said detectedfirst area, which is counted based on the reproduced signal from saidoptical disk upon reproducing information recorded on a further trackincluding said first area and adjacent to said track.